Someone in marketing announced it was premiering in the US in December 2016, but when they asked Tartakovsky and producers, they said no, not until early spring. So probably late February/March.

The thing is, IMDb is user-contributed, and it is also full of A-holes, and some A-hole edited in a fake air date.
Genndy said they have fewer animators than the regular series, so it is taking longer to make and that the release was pushed back to an unspecified date in 2017.
And really if
THIS
had aired, after years and years of fans complaning there was no end and asking for mroe, don't you think there'd be far, far
FAR
mroe threads about the airing of the new episode?
Anyway, I'm off to submit a deletion request for that false airdate

The New Number 2: "Are you going to run?"
Number 6: "Like blazes. First chance I get."

Thanks. Usually IMDB release dates are pretty reliable. Roll on next march!

I wonder why they haven't made any official "We're not releasing this on 2016" announcement yet. It's obvious at this point that they won't.
Some BODY once told me.

It hasn't aired yet. I don't know why it is listed as if it already premiered, I think it premieres though in march 2017